In recent years, solid-state image sensors of CMOS type in which MOS transistors are utilized in pixel amplifier sections have come to be widely used in digital still cameras and video cameras. Signal transfer methods in CMOS-type solid-state image sensors include two known methods, as follows. The first method is a so-called rolling shutter scheme that involves transferring voltage signals of pixels to a vertical signal line, sequentially for each row. In such a rolling shutter scheme, the timings of signal transfer are offset for each row, and hence the exposure timings are likewise offset for each row. The second method is a so-called global shutter scheme that involves holding charge temporarily in in-pixel memories, to render simultaneous thereby the exposure timings of all pixels.
Solid-state image sensors have also been proposed wherein some or all of the pixels in an imaging element are configured in the form of pixels for distance measurement (hereafter, ranging pixels), to enable distance detection relying on a phase difference scheme. The phase difference scheme is a method that involves comparing images of light having passed through different regions on a pupil of an imaging optical system, and detecting distance through triangulation according to a stereo image. As a result, high-speed high-precision ranging is made possible since, unlike in conventional contrast methods, no lens need be moved in order to measure distance. Further, the signals acquired in the ranging pixels can be used as image signals for generating a captured image; and, accordingly, ranging can thus be performed simultaneously with imaging.
Patent literature 1 discloses a solid-state image sensor wherein the exposure timings upon ranging at all the ranging pixels of a solid-state image sensor can be rendered simultaneous by utilizing global shutter in the solid-state image sensor.
Patent literature 2 discloses a solid-state image sensor that is capable of high-precision ranging, regardless of the texture direction of a subject, by providing a plurality of types of ranging pixels having mutually different pupil division directions. Specifically, the pupil division direction is modified by varying the arrangement of photoelectric conversion units within the ranging pixels.